Compare the part numbers before you spend the money on a new jug, here's my list of bikes I'd think a cylinder will work from:
The XT (prior to 2001 when it was a plated cylinder), TT, TT-R, TW, YFM (4-moto) and YTM (tri-moto?) engines below 250 cc are basically the same from the crank up. Any of those bikes are a very likely compatable donor, compare part numbers on everything between the gaskets (base gasket, jug, piston, wrist pin, etc.) for confirmation. The gaskets and wrist pin must match the TT-R225, everything else just make sure it's from the same machine, you'll be set.
Maybe you'll luck out and the motor is just worn top end in which case I highly recommend a slightly higher compression piston, that info is here: http://www.thumperta..._1#entry9312401
For two hundred bones, I'd buy it even without the extra frames. Keep in mind, the plastics are only available from Yamaha, so I wouldn't dream too big on making it perfect, but it would be a good buddy/play bike.